Research and development for reducing power loss of an overall system have been accelerated in order to put wireless power feeding into practical use. In particular, a power feeding system called “direct-current (DC)-Resonance” is a system that causes resonance of an electromagnetic field to occur from DC to convert energy of electricity and energy of the electromagnetic field. A resonance field is created by intermittently applying DC electricity to a resonance mechanism to cause a power transmission resonance mechanism and a power receiving resonance mechanism to interact with each other for resonance. A DC resonance wireless power feeding system can reduce power loss by simplifying a power feeding process unlike an existing system of applying a high-frequency magnetic field to a resonator.
For example, International Publication No. 2013/133028 discloses a system of causing electromagnetic field resonance to occur from a DC voltage and wirelessly feeding electric power. The wireless power feeding system disclosed in International Publication No. 2013/133028 includes resonance mechanisms at both of a power transmission side and a power reception side and a resonant current flows through the resonance mechanisms. Furthermore, a switching element is turned ON/OFF to cause an AC current to flow through the resonance mechanisms and can be made to perform a zero voltage switching (ZVS) operation. In the case of employing a dual-transistor push-pull type, electric power can be supplied to the power reception side from the power transmission side by causing the AC current to flow through the resonance mechanisms from DC electricity in both of an ON period and an OFF period.